<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      * {
        margin: 0;
        padding: 0;
      }
      main {
        height: 100vh;
        width: 600px;
        background-color: pink;
        margin: auto;
      }
      .side {
        width: 40px;
        height: 200px;
        background-color: gray;
        position: fixed;
        top: 100px;
        left: 50%;
        margin-left: 306px;
      }
    </style>
  </head>
  <body>
    <main></main>
    <div class="side"></div>
  </body>
</html>
